The Fifth Asia/Oceania Meteorological Satellite Users Users’ Conference 19-21 November 2014, Shanghai, China STUDY S U OF O THE EXTREME RAINFALL N EVENTS V N S IN BANGLADESH USING TRMM A. T. M. Shafiul Azam1*, M. Rafiuddin1 and Hi hi Uyeda Hiroshi U d 2 1Department of Physics, Bangladesh University of Engineering g g and Technology, gy, Bangladesh. g 2Hydrospheric Atmospheric Research Center, Nagoya University, Japan. BUET The Fifth Asia/Oceania Meteorological Satellite Users Users’ Conference 19-21 November 2014, Shanghai, China STUDY S U OF O THE EXTREME RAINFALL N EVENTS V N S IN BANGLADESH USING TRMM A. T. M. Shafiul Azam1*, M. Rafiuddin1 and Hi hi Uyeda Hiroshi U d 2 1Department of Physics, Bangladesh University of Engineering g g and Technology, gy, Bangladesh. g 2Hydrospheric Atmospheric Research Center, Nagoya University, Japan. BUET Introduction Introduction Bangladesh is mainly an agricultural country and its economy strongly depends on the vagaries of the weather and in particular the extreme rainfall events. Access of rainfall causes flood. Less rainfall causes drought. ¤ Timely and well-distributed rainfall is essential for better crop production. d ti ¤ The erratic behavior of rainfall has an antagonistic effect. ¤ So the variability of extreme rainfall are very important for Bangladesh. Data — BMD three hourly rain gauge data from 34 station. — TRMM 3B42 V6 data. data — TRMM 3B42 V7 data. Study duration: 1998 to t 2010. 2010 Methods ¤ ¤ Different algorithm. GrADS and Surfer software are used. Rainfall threshold: Very Heavy ( > 88 mm/day) Heavy (44 - 88 mm/day) Moderately Heavy (23 - 43 mm/day) Moderate (11 - 22 mm/day) Light (2.5 - 10 mm/day) Location of rain gauge stations of BMD. Results and Discussion Comparison of daily rainfall measured by BMD, TRMM V6 and V7 35 Average Rainfall in mm/day (1998-2010) 30 Rainfall (mm) 25 BMD TRMM_V7 TRMM_V6 20 15 10 5 0 0 30 60 90 120 150 180 210 240 270 300 330 360 390 Days In annual case BMD : 6.69 mm/day TRMM 3B42 V6: 5.81 mm/day y TRMM 3B42 V7: 6.70 mm/year During monsoon BMD : 13.99 mm/day TRMM 3B42 V6: 11.87 mm/day y TRMM 3B42 V7: 13.99 mm/day CC BMD : V6 = 0.94 BMD : V7 = 0.95 CC BMD : V6 = 0.691 BMD : V7 = 0.934 Comparison of Monthly rainfall measured by BMD and TRMM 600 Average Rainfall BMD TRMM_V7 400 TRMM_V6 300 200 Dec Nov Oct Sep Aug Jul Jun May Apr Mar 0 Feb 100 Jan Rainfall (m mm/month) 500 Months TRMM V6 underestimated rainfall during g every y month of the year. During July it underestimate 17.34% (90.92mm) of rainfall than that of the BMD. TRMM V7 overestimated during January to August and underestimated during September to December. During June it overestimated by 1.88% (8.67mm). Comparison of Yearly rainfall measured by BMD and TRMM 3000 Yearly Variation of Rainfall (mm) Rainffall (mm/year) 2500 2000 1500 1000 1998 Ave-BMD Ave-TRMM V7 Ave-TRMM V6 2000 2002 2004 2006 2008 2010 Years In annual case BMD : 2442 mm/year TRMM 3B42 V6: 2120 mm/year TRMM 3B42 V7: 2444 mm/year During monsoon BMD : 1698 mm TRMM 3B42 V6: 1448 mm TRMM 3B42 V7: 1706 mm CC BMD : V6 = 0.75 BMD : V7 = 0 0.94 94 CC BMD : V6 = 0.72 BMD : V7 = 0 0.93 93 Anomaly of annual rainfall measured by TRMM V6 and V7 with BMD ¤ TRMM V6 data d t underestimated d ti t d in i the th southern th and d northern th partt off the country. ¤ TRMM V7 data underestimated in the southern and northeastern portion of the country. Variation reduced. Diurnal Variation of Rainfall Rainfall (mm m/3h) 500 ¤ BMD: Two peak at 06 and 15 LST. ¤ TRMM V6 and V7: Two peak at 03 and 15 LST. ¤ Morning: Northern and coastal region. ¤ Afternoon: Central part of the country. Diurnal Variation of Rainfall (1998-2010) 400 300 BMD 200 TRMM_7 100 TRMM_6 0 0 3 6 9 12 Hours 15 18 21 24 In the lower troposphere, the southeasterly is accelerated in the evening, and the wind direction exhibits the clockwise change during the night. This feature corresponds with the nocturnal jet, jet which can be a cause of the midnight-early morning rainfall peak in the northeastern part of Bangladesh. [Terao et. al, American Geophysical Union] Very Heavy Rainfall Events CC BMD : V6 = 0.80 BMD : V7 = 0.84 ¤ No. of events: BMD (4.10), V7 (4.8) and V6(3.67). 8 No. of Events Very Heavy Rainfall Events (1998-2010) 6 4 2 ¤ VHR events prominent in coastal region and northeastern part of Bangladesh. BMD TRMM_V7 TRMM_V6 0 1998 2000 2002 2004 Year 2006 2008 2010 ¤ At Teknaf BMD ➩ 12.3, TRMM V7 ➩ 9 and V6 ➩ 6.83 events. ¤ TRMM V7 detect more VHR events than that of BMD. Anomaly of VHRE measured by TRMM V6 and V7 with BMD ¤ TRMM V6 data d t underestimated d ti t d in i the th southern th and d north th eastern t and d northwestern portion the country. ¤ TRMM V7 data overestimated almost everywhere of the country except Feni, M. Court, Hatia, Sandwip, Cox's bazar and Teknaf. Heavy Rainfall Events 16 Heavy Rainfall Events No. of Eve ents 14 ¤ HR events: TRMM V7 > TRMM V6. ¤ No. of events: BMD (11.58), V7 (11.62) and V6(9.6). 12 ¤ HR events prominent in coastal region and northeastern part of Bangladesh. TRMM also detect more HR events in the hill tracts area. 10 8 6 4 1998 CC BMD : V6 = 0.76 BMD : V7 = 0.91 BMD TRMM_V7 TRMM V6 TRMM_V6 2000 2002 2004 Days 2006 2008 2010 ¤ At Teknaf BMD ➩ 22.46, TRMM V7 ➩ 17.31 and at Sandwip V6 ➩ 14.46 events. Anomaly of HRE measured by TRMM V6 and V7 with BMD ¤ TRMM V6 data underestimated in almost all over the country. ¤ TRMM V7 data underestimated on southern and northern part of the country. country Moderately Heavy Rainfall Events No. of Events 22 20 Moderately Heavy Rainfall eVENTS (1998-2010) 18 ¤ Coastal region and northeastern part of Bangladesh. 16 14 12 BMD TRMM_V7 TRMM V6 TRMM_V6 ¤ At Sylhet BMD ➩ 31.31, TRMM V7 ➩ 24.08 and V6 ➩24.79 24 79 events. t 10 1998 2000 2002 ¤ MHR events: TRMM V7 > TRMM V6. ¤ MHR events: BMD (18.51), V7 (17.23) and V6(15.62). 2004 Year 2006 2008 2010 ¤ MHR events decreases from eastern part to western part. Anomaly of MHRE measured by TRMM V6 and V7 with BMD ¤ TRMM V6 data underestimated in almost all over the country except Ishurdi, Srimangol and Mymensingh. ¤ TRMM V7 data underestimated on southern and northern part of the country. Moderate Rainfall Events 30 ¤ MR events: TRMM V7 > TRMM V6. ¤ MR events: BMD (23.52), V7 (21.59) and V6(20.87). Moderate Rainfall Events (1998-2010) No. of events 27 24 ¤ Northeastern part of Bangladesh Bangladesh. 21 ¤ At Sylhet BMD ➩ 34.15, V6 ➩29.08 and at Srimongal TRMM V7 ➩ 27.67 events. BMD 18 TRMM_V7 ¤ MR events decreases from eastern part to western part. TRMM_V6 15 1998 2000 2002 2004 Year 2006 2008 2010 Anomaly of MRE measured by TRMM V6 and V7 with BMD ¤ TRMM V6 data underestimated in almost all over the country y except p northwest portion of the country. ¤ TRMM V7 data underestimated in almost every where of the country except northwest portion, portion central and some coastal portion of the country. Light Rainfall Events 50 ¤ LR events: TRMM V7 < TRMM V6. ¤ LR events: BMD (46.83), V7 (51.25) and V6(46.33). Light Rainfall Events (1998-2010) 45 ¤ BMD ➩ Eastern part TRMM V7 ➩Southeastern portion No. of Events 40 35 30 ¤ At Rangamati BMD ➩ 46.83 and at Srimongal TRMM V7 ➩ 51.15 51 15 LR events. events BMD TRMM_V7 25 TRMM_V6 ¤ Variation over country is less. 20 1998 2000 2002 2004 Years 2006 2008 2010 Anomaly of LRE measured by TRMM V6 and V7 with BMD ¤ Both the TRMM V6 and V7 overestimated on the southeastern and north western part of the country, on the other hand both of them underestimated on the western, central and northeastern part of the country. Summary ¤ In annual case TRMM V7 detects 0.08% more rainfall and V6 detects 13.19% % less rainfall than that of BMD observation data. ¤ TRMM V7 overestimate 16.91% and V6 underestimate 10.45% of VHRE. ¤ TRMM V7 overestimate ti t 0.36% 0 36% and d V6 underestimate d ti t 17.13% 17 13% off HRE. HRE ¤ TRMM V7 underestimate 6.90% and V6 underestimate 15.62% of MHRE. ¤ TRMM V7 underestimate 8.23% and V6 underestimate 11.28% of MRE. ¤ TRMM V7 underestimate 5.22% and V6 underestimate 0.12% of LRE. ¤ TRMM V7 detects more very heavy, heavy, moderately heavy and moderate rainfall events than that of TRMM 3B42 V6 data. ¤ TRMM V7 detects d t t less l li ht rainfall light i f ll events t than th TRMM V6 data. d t ¤ Very heavy and heavy rainfall events are dominated in the coastal part and northeastern part of the country. ¤ Moderately heavy and moderate rainfall events are dominated in the coastal and eastern part of the country. ¤ Light rainfall events occurred in all over the country and is more in th eastern the t partt off the th country. t ¤ The nocturnal jet may be a cause of the midnight-early morning rainfall peak in the northeastern part of Bangladesh. Bangladesh ¤ Yearly variation of rainfall events are very much similar measured by BMD rain gauge and TRMM V7 data. data Consequently, Consequently satellite data (TRMM V7) may be usable by meteorologist for different research purpose. THANK YOU THANK YOU THANK YOU
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